This research has two main components: (1) fundamental basic science experiments, aimed at understanding how and under what conditions surfactant-like molecules such as lysolipids exchange with lipid bilayers, form defects such as pores, modify the behavior of electropores, and ultimately disrupt the bilayer, and (2) direct clinical applications, with the goal of developing new and more rational protocols to provide higher yields for genetic transfection. With regard to the basis science aspect, the transport of surfactants will be characterized as they move to, from and within synthetic and natural lipid membranes. In Specific Aim #1 (SA1), we will investigate the sequence of steps involved in the molecular exchange of surfactant lipids with lipid bilayer vesicles. These steps include: transport through the aqueous media, intercalation into the outer lipid monolayer, intrabilayer transfer to the inner monolayer, and desorption from either bilayer interface. The amount and rate of surfactant exchange with the lipid bilayer will be measured by micropipet manipulation techniques in terms of the relative area change of single bilayer vesicles supported by micropipet suction. The role of a variety of conditions will be evaluated, ranging from: the concentration of surfactant; the rate of delivery of surfactant to the vesicle surface; the chemical nature of the surfactant (headgroup size, charge, attached polymer moieties like polyethylene glycol, as well as hydrocarbon chain length and saturation); and the chemical and physical nature of the bilayer (compressibility, gel or liquid crystalline phase, charged and polymeric headgroups). In this first SA, molecular interactions will also be studied between model ligands (avidin) and receptors (biotin) at the lipid bilayer surface. In SA2, two types of porous defect will be characterized, formed either by intercalation of certain surfactants (nanopores) or by the action of an electric field (micropores). Pore size and pore line tension will be measured as a function of the chemical nature and concentration of the exchanging surfactant. In SA3, the same experiments established in SAs 1&2 will be carried out on various model natural membranes, such as erythrocytes, erythrocyte ghosts and membrane vesicles in order to determine whether surfactant exchange and defect formation in natural biological membranes is similar to that observed in lipid bilayer membranes. Regarding the clinical application, gene transfection is now a burgeoning scientific and medical endeavor. In SA4, experiments will be conducted in our own laboratory and with BTX Inc., and two gene transfection research groups here at Duke. New strategies will focus on the use of electroporation to form resealable pores in surfactant-modified cell membranes through which genetic material can be selectively delivered to the interior of the cell. It is expected that this work will help researchers and clinicians to genetically manipulate cells for scientific study and to develop new anti-cancer and anti-HIV treatments.